We need the code for summation of the series up to nth term in javascript :
1/(2n+1)
When I executed the function series(80); it alerted NaN.
Code:
function series(n){
var i;
var s;
for(i = 1; i <= n; i++) {
s = s + 1/(2*i+1);
}
alert(s);
}
series(80);
You could set the default value on s = 0
function series(n) {
var i;
var s = 0;
var n;
for (i = 1; i <= n; i++) {
s = s + 1 / (2 * i + 1);
}
alert(s);
}
series(80)
Here is the example and definitely worked no need to declare n because we pass it as argument in function.
function series(n) {
var i, s = 0;
for(i = 1; i <= n; i++) {
s = s + 1/(2*i+1);
}
alert(s);
}
series(80);
https://jsfiddle.net/x1ea748y/1/
The problems asks "given a string, find the longest non-repeating sub-string without repeating characters". I am a little stumped why returning my code is not working for the string "dvdf" for example. Here is my code :
function lengthOfLongestSubstring(check) {
var letters = check.split("");
var max = 0;
var result = [];
for (var i = 0; i < letters.length; i++) {
var start = i
if (result.indexOf(letters[i]) === -1) {
result.push(letters[i])
} else {
i = i - 1
result = []
}
if (max === 0 || max < result.length) {
max = result.length
}
}
return max
}
This implementation gives the correct result for "dvdf".
It adds characters to current_string while there is no duplicate. When you find a duplicate cut current_string to the point of the duplicate. max is the max length current_string had at any time. This logic seems correct to me so I think it's correct.
function lengthOfLongestSubstring(string) {
var max = 0, current_string = "", i, char, pos;
for (i = 0; i < string.length; i += 1) {
char = string.charAt(i);
pos = current_string.indexOf(char);
if (pos !== -1) {
// cut "dv" to "v" when you see another "d"
current_string = current_string.substr(pos + 1);
}
current_string += char;
max = Math.max(max, current_string.length);
}
return max;
}
lengthOfLongestSubstring("dvdf"); // 3
The value of current_string in each round is "", "d", "dv", "vd", "vdf".
By replacing the result array with a map storing the last index for each encountered character, you can modify the loop body to jump back to one after the last index of an identical character and continue your search from there instead of just restarting from the current position via currently i = i - 1 which fails in cases such as 'dvdf':
Below is your code with changes to accommodate a map in place of an array:
function lengthOfLongestSubstring(check) {
var letters = check.split("");
var max = 0;
var result = new Map();
var start = 0;
for (var i = 0; i < letters.length; i++) {
if (!result.has(letters[i])) {
result.set(letters[i], i);
} else {
i = result.get(letters[i]);
result.clear();
}
if (max < result.size) {
max = result.size;
}
}
return max;
}
// Example:
console.log(lengthOfLongestSubstring("dvdf")); // 3
Here's a solution using Sliding window and HashMap.
var lengthOfLongestSubstring = function(str) {
if (!!!str.length || typeof str !== 'string') return 0;
if (str.length == 1) return 1;
let hashTable = {};
let longestSubstringLength = 0;
let start = 0;
for (let i = 0; i < str.length; i++) {
if (hashTable[str[i]] !== undefined && hashTable[str[i]] >= start) {
start = hashTable[str[i]] + 1;
}
hashTable[str[i]] = i;
longestSubstringLength = Math.max(longestSubstringLength, (i - start + 1))
}
return longestSubstringLength;
}
I figured out an easier solution:
function longestSubstring(str) {
let left = 0;
let max = 0;
let result = new Set();
for (let r = 0; r < str.length; r++) {
//The code will check for an existing item on the set
// If found, all the previously saved items will be deleted
// the set will return to being empty
while (result.has(str[r])) {
result.delete(str[left]);
left += 1;
}
result.add(str[r]);
max = Math.max(max, r - left + 1);
}
console.log(result);
return max;
}
console.log(longestSubstring('abcabccbc')); //3
Today (January 7th, 2021) this was the Leetcode question of the day. I initially used a solution very similar to the selected answer. Performance was okay but after reviewing the answer solution documentation I rewrote my answer using the sliding window technique (examples were only in Java and Python) since I was curious about how much of a performance improvement this would result in. It is slightly more performant (144ms versus 160ms) and has a lower memory footprint (42mb versus 44.9mb):
function lengthOfLongestSubstring(s: string): number {
let stringLength = s.length;
let maxLength = 0;
const charMap = new Map();
let pos = 0;
for (let i = 0; i < stringLength; i++) {
if (charMap.has(s[i])) {
pos = Math.max(charMap.get(s[i]), pos);
}
maxLength = Math.max(maxLength, i - pos + 1);
charMap.set(s[i], i + 1);
}
return maxLength;
}
console.log(lengthOfLongestSubstring("dvdf"));
Try this:
function lengthOfLongestSubstring (str) {
const map = new Map();
let max = 0;
let left = 0;
for (let right = 0; right < str.length; right++) {
const char = str[right];
if (map.get(char) >= left) left = map.get(char) + 1;
else max = Math.max(max, right - left + 1);
map.set(char, right);
}
return max;
}
You can try this:
function lengthOfLongestSubstring(str) {
let longest = "";
for (let i = 0; i < str.length; i++) {
if (longest.includes(str[i])) {
return longest.length
} else {
longest += str[i];
}
}
return longest.length;
}
console.log(lengthOfLongestSubstring("abcabcbb"));
console.log(lengthOfLongestSubstring("bbbbb"));
console.log(lengthOfLongestSubstring("abcdef"));
console.log(lengthOfLongestSubstring(""));
reset i to i -1 is incorrect. you need another loop inside the for loop. you try something like this (i didn't check the index carefully).
function lengthOfLongestSubstring(check){
var letters = check.split("");
var max = 0;
for (var i = 0; i < letters.length; i++) {
var result = [];
var j = i;
for(;j < letters.length; j++) {
if (result.indexOf(letters[j]) === -1) {
result.push(letters[j]);
} else {
break;
}
}
if(j - i > max) {
max = j - i;
}
}
return max;
}
You can try sliding window pattern to solve this problem.
function lengthOfLongestSubstring(str) {
let longest = 0;
let longestStr = "";
let seen = {};
let start = 0;
let next = 0;
while (next < str.length) {
// Take current character from string
let char = str[next];
// If current character is already present in map
if (seen[char]) {
// Check if start index is greater than current character's last index
start = Math.max(start, seen[char]);
}
// If new substring is longer than older
if (longest < next - start + 1) {
longest = next - start + 1;
// Take slice of longer substring
longestStr = str.slice(start, next + 1);
}
// Update current characters index
seen[char] = next + 1;
// Move to next character
next++;
}
console.log(str, "->", longestStr, "->", longest);
return longest;
}
lengthOfLongestSubstring("dvdfvev");
lengthOfLongestSubstring("hello");
lengthOfLongestSubstring("1212312344");
Find Longest Unique Substring using Map Method
var str = "aaabcbdeaf";
var start = 0;
var map = new Map();
var maxLength = 0;
var longStr = '';
for(next =0; next< str.length ; next++){
if(map.has(str[next])){
map.set(str[next],map.get(str[next])+1);
start = Math.max(start,map.get(str[next]));
}
if(maxLength < next-start+1){
maxLength = next-start+1;
longStr = str.slice(start,next+1);
}
map.set(str[next],next);
}
console.log(longStr);
You can try something like that:
function maxSubstring(s) {
const array = []
const lengthS = s.length
const pusher = (value) => {
if (value !== '') {
if (array.length > 0) {
if (array.indexOf(value) === -1) {
array.push(value)
}
} else {
array.push(value)
}
}
}
pusher(s)
for (const [index, value] of s.split('').entries()) {
let length = lengthS
let string = s
const indexO = s.indexOf(value)
pusher(value)
while (length > indexO) {
pusher(string.slice(index-1, length + 1))
length = --length
}
string = s.slice(index, lengthS)
}
array.sort()
return array.pop()
}
console.log(maxSubstring('banana'))
console.log(maxSubstring('fgjashore'))
console.log(maxSubstring('xyzabcd'))
Find Longest unique substring without using MAP(). Just simple slice().
The same can be used to return longest unique string.
Just replace "return max => return str"
const string = "dvdf";
var lengthOfLongestSubstring = function() {
if(string.length == 1) return 1;
if(string.length == 0) return 0;
let max = 0,i = 0, str = "";
while(i < string.length){
const index = str.indexOf(string.charAt(i));
if(index > -1) {
// s = "fiterm".slice(1,4) => ite
str = str.slice(index + 1, string.length);
}
str += string.charAt(i);
max = Math.max(str.length, max);
i++;
}
return max;
};
Logest unqiue substring:
function lengthOfLongestSubstring(s) {
if(s.length < 2) {
return s.length;
}
let longestLength = 1;
let currentStr = '';
for(let i=0 ; i < s.length ; i++){
if(currentStr.includes(s.charAt(i))){
let firstSeen = currentStr.indexOf(s.charAt(i));
currentStr = currentStr.substring(firstSeen+1,currentStr.length);
}
currentStr += s.charAt(i);
longestLength = Math.max(currentStr.length,longestLength);
}
return longestLength;
};
One liner with reduce method.
const subStrOfUniqueChar = str => [...str].reduce((p,c) => ( p.includes(c) ? (p += c, p.substr(p.indexOf(c)+1)) : p += c),'');
console.log(subStrOfUniqueChar('dvdf').length);
function lengthOfLongestSubstring(s: string): number {
const arr = s.split("");
let longest = 0;
const set: Set<string> = new Set();
for (let i = 0; i < arr.length; i++) {
set.add(arr[i]);
let tryIndex = i + 1;
while (arr[tryIndex] && !set.has(arr[tryIndex])) {
set.add(arr[tryIndex]);
tryIndex++;
}
if (set.size > longest) {
longest = set.size;
}
set.clear();
}
return longest;
}
I wanted to toss my hat in this ring because I feel like I've found a pretty creative solution to this. No if/else blocks are needed as the substring.indexOf() will attempt to find the matching string character in the array and delete the indexes of the array up to, and including, the match (+1). If an indexOf() call finds no match it will return a -1, which added to +1 becomes a .splice(0,0) which will remove nothing. The final Math check factors in the last character addition in the loop to determine which outcome is higher.
const findSubstring = string => {
let substring = [];
let maxCount = 0;
for (let i = 0; i < string.length; i++) {
maxCount = Math.max(substring.length, maxCount);
substring.splice(0, substring.indexOf(string[i]) + 1);
substring.push(string[i]);
}
maxCount = Math.max(substring.length, maxCount);
return maxCount;
}
uses sliding window concept
function lengthOfLongestSubstring(s) {
var letters = s.split("");
var subStr = "";
var result = [];
var len = 0;
let maxLen = 0;
for (var i = 0; i < letters.length; i++) {
const position = result.indexOf(letters[i]);
if (position === -1) {
result.push(letters[i]);
len += 1;
} else if (letters[i]) {
result = result.splice(position + 1);
len = result.length + 1;
result.push(letters[i]);
}
maxLen = len > maxLen ? len : maxLen;
}
return maxLen;
}
console.log(lengthOfLongestSubstring(" "));
Sliding Window Technique O(n)
you can use hash or Map in
loop through string char
Maintain dictionary of unique char
if char exist in memory take clear hash update the count in longest variable and clear count
start from first repeated char + 1 again.
var lengthOfLongestSubstring = function(s) {
if(s.length<2) return s.length;
let longest = 0;
let count=0;
let hash={}
for (let i = 0; i < s.length; i++) {
//If char exist in hash
if(hash[s[i]]!=undefined){
i=hash[s[i]];
hash={}
longest = Math.max(longest, count);
count = 0;
}else{
hash[s[i]]=i
count = count+1;
}
}
return Math.max(longest, count);
};
console.log(lengthOfLongestSubstring("abcabcbb"))
console.log(lengthOfLongestSubstring("au"))
My code isn't working . I'm trying to figure out what the bug is . Can someone help ? ! It's a function that is supposed to return an array of the first n triangular numbers.
For example, listTriangularNumbers(5) returns [1,3,6,10,15].
function listTriangularNumbers(n) {
var num;
var array = [];
for (i = 1; i <= n; ++i) {
num = i;
for (j = i; j >= 1; --j) {
num = num + j;
}
array.push(num);
}
return array;
}
Your initial initialization of j is wrong, it's starting at i so it's going too high. Also switched the operators around to make sure the conditions work.
function listTriangularNumbers(n) {
var num;
var array = [];
for (i = 1; i <= n; i++) {
num = i;
for (j = i-1; j >= 1; j--) {
num = num + j;
}
array.push(num);
}
return array;
}
You can try below code to get help:
a = listTriangularNumbers(8);
console.log(a);
function listTriangularNumbers(n) {
var num;
var array = [0];
for (i = 1; i <= n; i++) {
num = 0;
for (j = 1; j <= i; j++) {
num = num + j;
}
array.push(num);
}
return array;
}
You actually don't need 2 for-loops to do this operation. A single for-loop would suffice.
function listTriangularNumbers(n) {
// Initialize result array with first element already inserted
var result = [1];
// Starting the loop from i=2, we sum the value of i
// with the last inserted element in the array.
// Then we push the result in the array
for (i = 2; i <= n; i++) {
result.push(result[result.length - 1] + i);
}
// Return the result
return result;
}
console.log(listTriangularNumbers(5));
function listTriangularNumbers(n) {
var num;
var array = [];
for (i = 1; i <= n; ++i) {
num = i;
for (j = i-1; j >= 1; --j) {
num = num + j;
}
array.push(num);
}
return array;
}
var print=listTriangularNumbers(5);
console.log(print);
I am filling an array with random numbers with a loop, but the random number is exactly the same for each item in the array, I think this is because of the seed value that Math.rand() uses. How can i get a different number each time?
for(var i = 0; i < 10; i++){
number[i] = getRandom(0, 100);
}
function getRandom(a, b){
var num = Math.floor((Math.random()*b)+a);
return num;
}
Works fine for me:
http://jsfiddle.net/kzUUt/
You need to declare number though...
var number = new Array(10);
for(var i = 0; i < 10; i++)
{
number[i] = getRandom(0, 100);
console.log(number[i]);
}
function getRandom(a, b)
{
var num = Math.floor((Math.random()*b)+a);
return num;
}
Here is working demo.
var number = new Array();
for (var i = 0; i < 10; i++) {
number[i] = getRandom(0, 100);
}
function getRandom(a, b) {
return Math.floor((Math.random() * b) + a);
}
for (var j = 0; j < 10; j++) {
alert(number[j]);
}
I am having a problem with my code, I have not been able to figure it out for the past 2 days.
/**
*
*///function 7
/**
* returns the number of times that pattern occurs in string
*/
function score(string,pattern) {
var v = string.toUpperCase();
var s = pattern.toUpperCase();
var result = [];
for (var i = 0; i < string.length; i++) {
var index = v.indexOf(s, i);
if (index != -1) {
result[result.length]=index;
i = index;
}
}
return result.length;
}
/**
* returns an array of records of the form {trackTitle: ..., trackLyrics: ..., trackScore: ...} derived from web.
* Each record contains the track title, track lyrics and pattern score of its corresponding content.
*
*
*
*/
//FUNCTION 9
function urlScores(music, pattern) {
var scoresArray = [];
for(var i = 0; i < music.length; i++) {
for(var j = 0; j < music[i].tracks.length; j++){
var itemScore = score(music[i].tracks[j].title, pattern) + score(music[i].tracks[j].lyrics, pattern);
if (itemScore > 0) {
scoresArray[scoresArray.length] = ({indexOfTrack: j, trackTitle: music[i].tracks[j].title, trackLyrics: music[i].tracks[j].lyrics, trackScore: itemScore, album: music[i]});
}
itemScore = 0;
}
}
return scoresArray;
}
/**
* Sorts the result of urlScores() into descending order.
* Records with a score of zero are omitted.
*/
//FUNCTION 10
function rankedScores(music, pattern) {
var scoresArray = urlScores(music, pattern);
function swap(a, b) {
var temp = scoresArray[a];
scoresArray[a] = scoresArray[b];
scoresArray[b] = temp;
}
for(var i = 0; i < scoresArray.length; i++) {
for(var x = 0; x < scoresArray.length - 1; x++) {
if (scoresArray[x].score > scoresArray[x + 1].score) {
swap(x, x + 1);
}
}
}
alert(scoresArray);
}
When I run it with the following:
rankedScores(albums, "sparrow");
The albums variable is - http://pastebin.com/G25SxrwY
The error is the following -
[object Object],[object Object]
Thank you very much!
That is not an error:
If you stringify an Array containing two objects, that is the supposed output.